Little is known about the functional benefits of strengthening exercises in older persons. The proposed project will experimentally determine if strengthening exercises for community-dwelling, disabled older men and women result in improvements in gait and other locomotor activities. The experimental plan proposes to study 100 disabled elders randomly assigned to 6 months strengthening exercises or no-exercise control. The general hypothesis is that disabled older persons compensate for strength impairments by substituting potentially destabilizing, quantifiable body postures and movement strategies, and that these compensations are reduced following strength gains. Proposed Specific Aims are: 1) to determine the body segment postures, momentum and compensatory strategies in disabled older persons. It is hypothesized that disabled older persons use excessive upper body momentum to substitute for lower limb weakness during locomotor activities; 2) to assess whether functional abilities improve following a 6 month lower limb strengthening program. It is speculated that following 6 months of strengthening exercise, subjects move about more rapidly and with greater stability than subjects in the control group, and that change in strength correlates (r>.8) directly with change in locomotor velocity and torques, and inversely with use of segmental momentum transfer during locomotor activities; and 3) to ascertain whether improvement in functional ability results in a change in disability. It is proposed that changes in functional abilities identified under Aim #2 will, in turn, result in improvements in disability during real life role activities.